(1) Field of the Invention
This invention relates to a female terminal metal fixture which is provided in a box-like body with a resilient contact tongue adapted to elastically contact with a tab of a male terminal metal fixture and in particular functions to prevent the resilient contact tongue from being excessively deflected.
(2) Statement of the Prior Art
A typical example of conventional female terminal metal fixtures which function to prevent a resilient contact tongue from being excessively deflected is disclosed in Japanese Utility Model Public Disclosure No. HEI 3-77382 (1991). For convenience of explanation, the conventional female terminal metal fixture disclosed in the above Disclosure will be described below by referring to FIGS. 19 to 21. FIG. 19 is a longitudinal sectional view of a conventional female terminal metal fixture. FIG. 20 is a longitudinal sectional view similar to FIG. 19, illustrating a position in which a tab is correctly inserted into a box-like body. FIG. 21 is a longitudinal sectional view similar to FIG. 19, illustrating a position in which the tab is incorrectly inserted into the box-like body.
As shown in FIG. 19, a box-like body 31 is provided on each side wall 32 with a projection 33, which is disposed below a distal end side of a resilient contact tongue 34 turned back rearwardly from a front end of a bottom wall, by punching up the side wall 32 inwardly in the body 31. When a tab 35 of a mating male terminal metal fixture is inserted into the body 31 from its front end, the tab 35 is inserted into an insertion space 38 defined in the body 31 between the resilient contact tongue 34 and a ceiling wall 36, as shown in FIG. 20, while deflecting the resilient contact tongue 34 downwardly so that the tongue 34 does not contact with the projection 33, if an insertion direction is correct. However, if an insertion angle is not so great, the resilient contact tongue 34 is borne by the projection 33 before the deflection of the tongue 34 exceeds its elastic limit, thereby preventing a further deflection of the tongue 34 in a downward direction. That is, it is possible to prevent the resilient contact tongue 34 from being extremely deflected and from reaching a plastic deformation.
However, if the insertion angle of the tab 35 becomes great, the distal end of the tab 35 abuts on the resilient contact tongue 34 at a position between a turn-back portion 37 and a contact point on the projection 33, for example, a position shown in FIG. 21. Since the tongue 34 is not borne at this position, the tongue 34 will be readily brought into plastic deformation when the tab 35 pushes down the tongue 34 strongly.
On the other hand, to overcome this problem, Japanese Patent Public Disclosure No. HEI 6-60931 (1994) discloses a female terminal metal fixture in which a horizontally extending projection is formed on each side wall of a box-like body by punching up the wall inwardly in the body. The projections can support a resilient contact tongue at its distal end side point and its middle point, thereby preventing the tongue from being extremely deflected. However, the box-like body will be weakened at its side walls since the side walls are punched up over a wide range.
Still another conventional female terminal metal fixture will be described below by referring to FIGS. 22 to 24, for convenience of explanation.
FIG. 22 is a longitudinal sectional view of still another conventional female terminal metal fixture. FIG. 23 is a longitudinal sectional view similar to FIG. 22, illustrating a position in which a tab is correctly inserted into a box-like body. FIG. 24 is a longitudinal sectional view similar to FIG. 22, illustrating a position in which the tab is incorrectly inserted into a box-like body.
The female terminal metal fixture, as shown in FIG. 22, includes a box-like body 31 and a resilient contact tongue 34 in the body 31, which is adapted to elastically contact with a tab 35 of a male terminal metal fixture. The resilient contact tongue 34 has a turn-back portion 37, which is formed by inwardly bending an elongated plate extending from a front end of a bottom wall 40 of the body 31 in a manner of a hair pin, and a curved portion 39, which is formed by outwardly bending a distal end of the tongue 34. The box-like body 31 encloses the resilient contact tongue 34.
When the tab 35 of the male terminal metal fixture is inserted through a front opening in the body 31 into an insertion space 38 defined between the resilient contact tongue 34 and a ceiling wall 36 of the body 31, the tab 35 contacts with the resilient contact tongue 34 elastically and electrically, as shown in FIG. 23. However, if the resilient contact tongue 34 is permitted to be freely deformed, insertion of a foreign substance causes the resilient contact tongue 34 to be deformed over an elastic limit. This results in poor connection between the male and female terminal metal fixtures. Heretofore, there have been several means for preventing excess deflection of the resilient contact tongue 34. For example, the curved portion 39 shown in FIG. 22 was provided.
However, any foreign substance becomes trapped in the insertion space 38, because the conventional means for preventing excess deformation are provided on the resilient contact tongue itself. There are some cases in which even the curved portion 39 cannot prevent excess deformation of the tongue 34.
For instance, in the case that dust such as metallic chips are attached to a top face of the tab 35 (such dust comprises a foreign substance), the tab is increased in thickness. When such a tab having increased thickness is inserted into the box-like body, the tab deforms the resilient contact tongue over its elastic limit. Also, any errors caused during producing processes will bring about an increased thickness over a standard thickness into the tab.
In the case that alignment of the fixtures comes out of a standard over unexpectedly, an insertion angle of the tab 35 to the female terminal metal fixture becomes greater as shown in FIG. 24 and the distal end of the tab 35 abuts near the turn-back portion 37 of the resilient contact tongue 34. Thus, it is impossible to avoid excess deformation of the tab because the tab is not borne at the abutting position.